Your vet has diagnosed or suspects your dog has a painful tearing of the cranial cruciate ligament (CrCL), one of the most important ligaments in the dog’s knee joint. CrCL problems are the most common orthopaedic problem in dogs, with the many options available for treatment often making decisions confusing for owners. We offer several options for treatment catering to different patients, clients and budgets. 

The team of surgical vets and veterinary nurses at Rangiora Vet Centre hope to be able to help guide you through the decision-making process for your dog’s treatment. We start this process with a consultation to assess and discuss your dog’s problem and the treatment options. This can be done as a stand-alone appointment for those owners who would like additional time and information to help their decision-making, or on the day of a scheduled x-ray or surgery for those owners who wish to reduce the number of visits with their pet.

We hope the following information can help provide you with a starting point to understand your dogs’ condition, as well as the surgical options available, and look forward to meeting you and your dog soon.

What is the CrCL, why is it so important?

In humans this same ligament is known as the Anterior Cruciate Ligament (ACL) and is also a common site of injury, often in skiers and sports-people. Although in humans ACL injuries can sometimes be managed without surgery, the mechanics of the canine knee differ slightly, dogs stand on a flexed knee as if walking on tip-toes.

When healthy, the dogs knee joint should act as a simple hinge, like ours, swinging just two ways, forward and backward. The cranial and caudal cruciate ligaments are at the centre of this hinge, inside the stifle joint, and keep the femur (thigh bone) in alignment with the tibia (shin bone) during motion. These two ligaments, in the shape of a cross, maintain appropriate contact between the two bones. The illustration shows the location of both ligaments.

The CrCL attaches in the back of the femur and comes forward to attach to the front of the tibia. The caudal cruciate ligament attaches on the front of the femur, and goes backwards to attach to the back of the tibia. Where they cross each other is the “hinge” point.

What’s happened when the ‘cruciate has gone’?

Consider the cruciate ligament to be a rope made of many fibres.

When diagnosed with a cruciate rupture this means that the rope has either snapped and undergone tearing of all the fibres (this is called a complete tear and is most likely caused from trauma) or only some of the fibres have torn (referred to as a partial tear). For the majority of dogs the disease is degenerative (slowly progressive) and the ligament will slowly fail over weeks to years before rupturing.

Dogs have a backward slope on the tibial plateau (the top upward-facing surface of the bone). The joint is under shear forces when weightbearing, with the femur wanting to slip down the slope. The cranial cruciate ligament usually stops any caudal movement of the femur down this slope but with damage to the cruciate ligament instability develops and the femur slides backwards down the slope. It is this mechanical instability which is the main cause of your dog’s lameness. The fancy term for this phenomenon is “cranial tibial subluxation” - as the femur moves backward the tibia is pushed forward. The bottom line is that it hurts!

Two sensitive cartilage cushions called menisci sit between the two bones and act as tiny shock absorbers. They are delicate and sensitive, and often injured in CrCL disease, causing additional pain. The sooner we are able to diagnose this progressive problem the better the result can be for your dog. At surgery, we inspect the joint and remove any damaged cartilage and the remnants of the cruciate ligament.

Huge amounts of scientific research has been undertaken to try understand why this ligament fails in so many dogs, and it appears to be a complex interaction of the limb conformation, breed and genetics, bodyweight, exercise patterns, trauma and other factors..... there is no one answer!!

What’s the best treatment for my dog?

Because this is a common problem, we have a lot of research studies to draw on looking at outcomes for dogs with CrCL problems. In the past, we used to think that some smaller dogs may not require surgery, however we now know that all sizes and breeds of dog will do better with surgical stabilisation of their joint than without.

We are trained, experienced and equipped for several different procedures to manage this disease, with each having advantages and disadvantages. The surgeon will discuss the different options with you and help establish the best treatment plan for your dog and your family, with financial considerations taken into account.

The aim of all surgical procedures is to eliminate the ‘cranial tibial subluxation” shown in the earlier diagram to stabilise the joint and stop the pain. The names of each surgery can be confusing. The two broad categories are:

1. surgeries that change the geometry of the stifle so that the CrCL is not needed

and

2. surgeries that attempt to replace the ligament with a synthetic replacement.

Option 1a: “Tibial Plateau Levelling” procedure

Levelling of the tibial plateau is our preferred option for the majority of dogs. It involves reducing the slope of the joint surface at the top of the tibia to make it nearly flat. Outcomes are predicted to be 90-95% of normal limb function, with rapid return to limb use. For sporting or working dogs we strongly recommend this option.

Specific planning radiographs are taken to establish the degree of rotation needed. The surgery involves a single curved cut of the tibia and a rotation of the joint through those calculated degrees. The tibia is then stabilised with a bone plate and screws. The result is that the force which pushes the lower limb forwards when the animal bears weight is removed, eliminating abnormal strain on the joint. By levelling the weight bearing surface of the tibia we have “redesigned” the joint so it no longer needs a CrCL.

A Tibial Plateau Levelling procedure has been shown to arrest the tearing process in dogs with partial tears of the CrCL if performed early enough. The procedure “off-loads” the remaining ligament, allowing it to heal. There have been no studies showing any other surgical procedure can achieve this goal for these dogs.

Option 1b: Tibial Tuberosity Advancement

The TTA procedure was developed in Switzerland. It is based on biomechanical studies that show the forces through the stifle joint being directed parallel to the patella tendon when standing. By advancing the patella tendon to be 90O to the tibial slope shear forces are eliminated and the stifle is stable.

At surgery the tibial tuberosity is cut along a pre-measured line and the tibial tuberosity is advanced forward a pre-determined distance (measurements made pre-operatively from the radiographs). The titanium implants of a cage and plate hold the tibial tuberosity in its advanced position. This prevents the instability between the femur and the tibia when weightbearing.

Titanium is osteoconductive which allows for rapid bone remodelling around and through the implants promoting more rapid healing. Recovery time is potentially shorter than for other procedures and they can begin exercising sooner however patients still require a minimum of 6 weeks restricted activity.

Option 2: “Ligament replacement” procedure

Placing a synthetic implant to do the job of the ruptured ligament can also help stabilise the joint, reduce pain and improve joint function. Outcomes are predicted to be around 80-85% of dogs recovering near normal limb function, and the return to limb use is a little longer than with levelling of the tibial plateau. This option can be applied to almost all dogs with CrCL rupture but is more suited to dogs that are under 15kg or dogs that do not have a steep tibial plateau angle. It is the older of the methods, but is the most cost effective option for owners with a tight budget, we still get consistently marked improvements over non-surgical treatment with this method.

Unfortunately, there is no “perfect” replacement, as the CrCL is located inside the dog’s knee joint, where placing a synthetic implant causes a lot of problems within the knee. So we locate the implant on the outside surface of the joint. We have 2 different implant systems for ligament replacement to suit different budgets.

Dogs with excessive slope

Some dogs have a very steep slope to their tibia which makes these methods above unsuitable for them. In these special cases we would have to consider two other procedures – either a TTO or a CWO. This will be discussed with you if found at the pre-operative radiographs.

What happens on the day?

All dogs will have an appointment for their owners and their surgeon either prior to surgery or on the morning of surgery to discuss the procedure in detail, cover any questions that may arise and decide on the ideal surgical technique. A surgical consultation is not a commitment to continue to surgery, and we are happy to discuss all options with owners without any obligation. This consultation will normally be 30-45 minutes.

On the day of surgery, patients are admitted between 8-8.30am. Surgery schedules and order of cases are determined on the day, so your pet’s procedure may be in the morning or afternoon. You will be updated on your pets timing for surgery, and those waiting for an afternoon spot will have a warm kennel and bed, walked regularly and offered water.

All patients receive an individualised anaesthetic protocol and a dedicated nurse anaesthetist is with your pet throughout the procedure. They will also have a pain prevention program planned which includes an epidural as well as oral and injectable painkillers.

Radiographs will be taken under anaesthesia, if not already performed, to assess the joint and allow the surgeon to make the correct measurements for planning surgery.

The procedure generally takes one and a half to two and a half hours, and once your pet is back in recovery, a member of the surgical team will contact you as soon as possible to let you know how the procedure went.

All pets undergoing orthopaedic surgery stay with us overnight. This allows us to provide them with up-to-date pain management and to monitor their recovery fully. A veterinary nurse remains on-site with them at all times. In general, patients are discharged mid to late afternoon the day following surgery.

What happens when my dog comes home?

When it is time for your pet to be reunited with you, one of our surgical nurses will meet with you to go over all the at home care your pet requires. This information will all be written down for you to take home. Patients are checked at 3-4 days post surgery (this will usually be with any one of our team of vets).

Regardless of surgical technique, all patients must carry out a minimum 6-8 week confinement period to ensure they get the best result.

The confinement required for good healing requires:

• No running

• No jumping or playing with other dogs

• Slippery surfaces and stairs must be avoided

Dogs who are not well confined risk not only delayed healing but other serious complications, so it’s important we get this right.

All dogs will have a check up at 8 weeks to determine if they are ready for further exercise. Dogs who have had a TTA or TPLO require an x-ray of their knee to check the progress of bone healing and that the implants are all sitting correctly. This is performed at 8 weeks following surgery (a bit later if older), and requires a little sedation, so your pet will need to be with us for the day.

We also highly recommend physiotherapy as rehabilitation for your pet. Most of the time the cost of the initial physiotherapy session is included in the cost of surgery. During this visit they will demonstrate a home programme for you to undertake with your pet. We encourage all patients to carry on with regular visits to the physiotherapist for the duration of their recovery if possible. Although we work very closely together, and their Rangiora branch is located at our clinic, Animal Physio NZ are a separate business to Rangiora Vet Centre, so please contact them directly to schedule your physio appointments.

www.animalphysionz.com Rangiora Clinic located at Rangiora Vet Centre 181 Lehmans Rd, Rangiora 03 420 2210